Spraying Assembly, and Sprayer Equipped with at least one such Assembly

ABSTRACT

A spraying assembly is provided. The spraying assembly includes at least one nozzle for liquid that is to be sprayed, and at least one active substance injector which is situated directly upstream from the at least one nozzle and to which liquid to be sprayed is supplied by a pump or a pressurized reservoir, with interposition of an obturator on a conduit connecting the pump or the pressurized reservoir to the injector. The spraying assembly also includes an outlet valve for each injector designed to close each outlet orifice. The present invention avoids overdosing or underdosing of the product that is to be sprayed as active substance.

The present invention relates to a spraying assembly, and a sprayer equipped with at least one such assembly.

BACKGROUND

A traditional agricultural sprayer, for example a tractor, includes a ramp equipped with a plurality of spray nozzles connected to ducts in which a liquid product to be sprayed on the plants to be treated circulates. The plants to be treated may be of any type, and the term “agricultural” is to be understood here in the broad sense, in particular including arboricultural crops.

In the case of a direct injection spraying system, an active liquid or powdery material is incorporated or mixed into the liquid to be sprayed (in general clean water) upstream of the ramp, over the course of the spraying, as considered in WO-A-90/11010, where a ball-shaped check valve is installed at the outlet of a dosing pump relatively remote from the nozzles it supplies.

Such a system has a certain number of drawbacks.

When the sprayer slows down, the flow rate of the injection of active substance into the liquid to be sprayed decreases.

However, in particular in the case of a very long ramp, the liquid with a smaller dose of active substance takes some time to reach the nozzles, and during that time the plants are overdosed with active substance. The ramp causes inertia in the dosing of the mixture of active substance and liquid to be sprayed.

Conversely, when the sprayer accelerates, the injection flow rate of active substance into the liquid to be sprayed increases.

The liquid with a higher dose of the active substance takes some time to reach the nozzles, and during that time, the plants are underdosed with active substance.

Furthermore, during the modification of the speed of the sprayer, these overdosing or underdosing phenomena overlap, which accumulates, amplifying them and their respective negative effects described above.

It has also been possible to observe that the overdosing or underdosing phenomena were irregular and asynchronous, depending on the distance of each nozzle relative to the point of the incorporation of the active substance into the liquid to be sprayed, in particular in the case of very long ramps.

Furthermore, when the spraying is restarted by a ramp segment comprising several nozzles after a temporary interruption in that spraying, the liquid that initially flows in the duct results from dosing done before that interruption. However, such dosing generally does not correspond to the required dosing after that restart, since the speed of the sprayer changes relatively often.

WO-A-2005/048704 describes a spraying assembly comprising a nozzle for projecting a liquid to be sprayed and active substance pumps that are located directly upstream of the nozzle, to introduce the active substance into a mixing area with the liquid to be sprayed.

However, the pumping chamber of each active substance pump is in permanent fluid communication with said mixing zone. Yet although the volume of that pumping chamber is substantially smaller than the volume of the ramp, it also causes a certain volume inertia in the dosing of the mixture to be produced, which prevents the spraying assembly from making quick, or even instantaneous, variations in the concentration of said mixture and leads to overdoses.

SUMMARY OF THE INVENTION

An objection of the present invention aims to resolve these drawbacks by proposing a spraying assembly and a sprayer that are very reactive and reliable, and relatively easy to adjust remotely, potentially electronically.

To that end, the present invention provides a spraying assembly comprising at least one nozzle for liquid that is to be sprayed, and at least one active substance injector into the liquid that is to be sprayed, the injector being situated directly upstream from at least one nozzle and supplied with liquid to be sprayed by means of a pump or a pressurized reservoir, with interposition of an obturator on a conduit connecting the pump or the pressurized reservoir to the injector. This assembly additionally comprises, for each injector, an outlet valve designed to close the or each outlet orifice.

Within the meaning of the present invention, the injector is situated directly upstream from the or each nozzle, i.e., the flow path of the active substance between the outlet of the injector and the nozzle has a length of only several centimeters.

Owing to these features, the assembly according to the invention makes it possible to incorporate the active substance into the liquid to be sprayed at the last minute, i.e. just upstream from a nozzle or a group of nozzles, and therefore just before the actual spraying of that liquid.

It is therefore possible to adjust the dosing of active substance in the liquid to be sprayed instantaneously, and consequently to avoid the overdoses or underdoses observed in the prior art.

According to other advantageous, but optional, features of the spraying assembly according to the invention, any one of the following features may be considered alone or according to any technically allowable combination:

-   -   the or each outlet valve is a needle adapted to come alongside a         seat formed at the outlet orifice;     -   the or each nozzle and the or each injector are mounted on the         same body or two adjacent bodies, a mixture of the liquid to be         sprayed with the active substance occurring through turbulence         in the or each body;     -   this assembly comprises a plurality of injectors situated         directly upstream from the or each nozzle;     -   this assembly comprises means for remotely controlling each         injector and/or each outlet valve, and the or each injector         and/or the or each outlet valve can be actuated remotely;     -   the or each injector is chosen from the group comprising a valve         or pump of the ceramic, electromagnetic, piezoelectric or         peristaltic type;     -   the assembly comprises means for injecting air into each         injector.

The present invention also provides a sprayer equipped with at least one assembly according to the present invention, comprising at least one primary conduit designed to supply the or each nozzle with liquid to be sprayed, and at least one secondary conduit designed to supply the or each injector with active substance.

According to other advantageous, but optional, features of the sprayer according to the invention, any one of the following features may considered alone or according to any technically allowable combination:

-   -   the sprayer comprises a plurality of secondary conduits         respectively supplying each injector;     -   the sprayer comprises means for keeping the pressure of the         liquid to be sprayed constant directly upstream of the or each         nozzle;     -   the sprayer comprises means for regulating the flow rate of         active substance in the or each body;     -   the sprayer comprises regulating means adapted to regulate the         flow rate of active substance in each injector as a function of         the displacement speed of the sprayer and/or the state of the         plant surface to be treated, for example depending on whether         the plants to be sprayed are healthy or in poor health;     -   each means for maintaining the pressure of the liquid to be         sprayed and each means for regulating the flow rate can be         actuated individually and independently;     -   the or each injector comprises a pump or a piezoelectric,         electromagnetic or peristaltic valve, and the control means are         adapted to vary the operating speed of the pump or the valve so         as to drive the flow rate thereof; and     -   at least one of the secondary conduits is adapted to convey a         first type of active substance, for example an herbicide         (potentially selective, and therefore dangerous for other         crops), and at least one other of the secondary conduits is         adapted to convey a second type of active substance, for example         an insecticide, a fungicide, or a wetting agent;     -   the or each primary conduit includes at least one valve to         control the circulation of liquid to be sprayed and the or each         secondary conduit includes at least one obturator to control the         circulation of active substance, the or each valve and the or         each obturator being able to be actuated remotely.

The present invention also provides a method for cleaning a spraying assembly in which means are provided for injecting air into each injector through its outlet orifice. This method comprises steps consisting of injecting a quantity of air into each injector, countercurrent from the direction of flow of the liquid to be sprayed in that injector, and pushing part of the liquid to be sprayed that is present in that injector and in its supply means back toward a storage reservoir for the product to be sprayed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be well understood, and advantages thereof will also emerge, in light of the following description, provided solely as a non-limiting example, in reference to the appended drawings, in which:

FIG. 1 is a diagram of the spraying assembly according to a first embodiment of the invention; and

FIG. 2 is a diagram similar to FIG. 1 of a spraying assembly according to a second embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a nozzle 1 mounted on a body 3 connected to a primary vat 5 by means of a shared conduit 78 and a primary conduit 7. The inlet of the shared conduit 78 is connected on the primary vat 5. The primary conduit 7 emerges in the body 3.

The term “connect” relates to a fluid communication, which means a conduit allowing the fluid to circulate between two components of a spraying assembly, for example between the primary vat 5 and the body 3. Such a conduit may be embodied by a flexible hose, a rigid tube, or any other known equivalent means.

Alternatively, the or each nozzle 1 and the or each injector 21 a to 21 d may be mounted on two adjacent bodies 3, i.e. close to one another.

The or each body 3 is adapted to produce a mixture of the liquid to be sprayed with the active substance. To that end, the or each body 3 may be equipped with a static mixer, baffles and/or propellers, etc. A valve 203 is arranged on the primary conduit 7 so as, if necessary, to prevent said mixture from returning into the primary conduit 7. Alternatively, the valve 203 may be replaced by a check valve.

The body 3 is in turn mounted on a spraying ramp structure 9.

The primary vat 5 and the ramp 9 are mounted on the chassis 11 of an agricultural sprayer, such as a tractor or trailer.

A primary pump 13 is arranged on the shared conduit 78 between the primary vat 5 and the body 3. The conduit 78 is said to be shared because it emerges, by means of a T coupling 210, on the one hand on the primary conduit 7 and on the other hand on a return conduit 8 designed to allow the liquid to be sprayed to circulate up to the primary vat 5.

The first spraying assembly includes a valve 207 and a valve 208 respectively arranged on the primary conduit 7 and on the return conduit 8 to control the circulation of liquid to be sprayed therein.

The valves 203, 207 and 208 are driven into the open position or closed position by suitable electrical means.

When the valve 207 is open, the liquid to be sprayed circulates in the primary conduit 7. When the valve 207 is closed, the liquid to be sprayed does not circulate in the primary conduit 7.

Likewise, when the valve 208 is open, the liquid to be sprayed circulates in the return conduit 8. When the valve 208 is closed, the liquid to be sprayed does not circulate in the return conduit 8, but flows in the primary conduit 7 if the valve 207 is open.

This spraying assembly can thus operate through recirculation, in particular to keep the liquid in motion even after having temporarily, partially or completely, interrupted the spraying thereof.

Several injectors 21 a, 21 b, 21 c and 21 d, four in the illustrated example, are mounted on the body 3 and each respectively connected to a secondary vat 25 a, 25 b, 25 c and 25 d by secondary conduits 27 a, 27 b, 27 c and 27 d.

Respective pumps 33 a, 33 b, 33 c and 33 d are located on the secondary conduits 27 a to 27 d.

The injectors 21 a to 21 d may be valves or may be ceramic or electromagnetic or piezoelectric pumps. Each of the injectors 21 a to 21 d can be actuated remotely, i.e., it may be controlled by suitable and remote electrical means.

Each injector 21 a, 21 b, 21 c and 21 d also includes a respective obturator or check valve 24 a, 24 b, 24 c and 24 d, in which a corresponding secondary conduit 23 a, 23 b, 23 c and 23 d is arranged so as to cut the supply.

Furthermore, the spraying assembly comprises outlet valves that are respectively arranged close to and downstream from each injector 21 a to 21 d so as to close off the outlet orifice 26 a to 26 d thereof. Each outlet valve is made up of a needle 22 a to 22 d with a conical, flat, or piston shape, adapted to come alongside a seat or bore with a complementary shape that is formed at the corresponding outlet orifice 26 a to 26 d.

Each needle 22 a to 22 d serves to allow or stop the fluid communication between the specific volume of the injector 21 a to 21 d able to contain active substance and the nozzle 1 or, more specifically, the body 3.

FIG. 1 shows a single body 3 supporting a single nozzle 1 and four injectors 21 a to 21 d, but the ramp 9 may be provided with a plurality of bodies 3 each supporting one or more nozzles 1 and one or more injectors 21.

Each of the bodies 3 is in fluid communication with the primary conduit 7, and each of the injectors 21 is in fluid communication with a secondary conduit 23 concerning it.

Means for creating turbulence are provided in the body 3. They favor mixing by turbulence between the liquid to be sprayed and the active substance leaving an injector 21.

Typically, the bodies 3 may be distributed at regular or irregular intervals as needed, for example every 50 cm on the ramp 9.

Alternatively, the bodies 3 may be mounted on independent segments of the ramp 9. A “segment” is a group of standard nozzles 1 that are successively arranged along the ramp 9 or juxtaposed on an independent branch, and whereof the nozzles can be controlled and operate simultaneously, when they are not controlled individually.

In a first embodiment, the secondary pumps 33 are typically adapted to generate a liquid pressure in the secondary conduits 23 a to 23 d that is higher than that prevailing in the primary conduit 7 and the body 3. This pressure may for example be approximately 10 bars.

In a second embodiment, there are no more pumps 33 and the cans 25 are kept at a slight overpressure, of several decibars, relative to the spraying pressure generated by the primary pump 13. This may for example be obtained using pneumatic or hydraulic pressure exchangers, with pistons or membranes but with different sections, situated between the circuits 7 and 23.

In order to control the size and spectrum of the sprayed crops, the agricultural sprayer also comprises means for keeping the pressure of the liquid to be sprayed constant directly upstream from each nozzle 1. Such means may for example be made up of valve or membrane regulators or other known equivalent means. The terms “upstream” and “downstream” refer to the flow direction of the considered fluid, i.e., the liquid to be sprayed, the active substance, or the mixture thereof.

The agricultural sprayer also comprises means for example, a regulator or valve, for regulating the flow rate of active substance in each secondary conduit 23 a to 23 d. The supply of each injector 21 a to 21 d with active substance therefore depends on these regulating means or regulators.

Such means for regulating the flow rate of the active substance, as well as the obturators 24 a to 24 d (in all or nothing mode), or the injectors 21 (in discrete variation mode, by electrical pulses) controlling the supply of liquid to be sprayed, may be controlled as a function of data supplied by a global positioning system (of the GPS type) or an onboard camera on the ramp or the agricultural vehicle coupled to an image processing system.

Such an image processing system makes it possible to detect adventives to be destroyed or to use the color of the plant to evaluate its needs with respect to the active substance for growth, such as fertilizers or growth regulators.

Furthermore, the active substance circuits may have structures and/or arrangements that differ as a function of the type of active substance they are respectively designed to convey.

Thus, each secondary vat 25 a to 25 d can be adapted to receive a predetermined type of active substance and each secondary conduit 23 a to 23 d may be adapted to convey the corresponding type of active substance.

For example, the secondary duct 23 a may be reserved to convey only selective herbicides (dangerous for other crops), while the secondary conduit 23 d may rather be adapted to convey fungicides or insecticides (the residues of which are not harmful for other crops).

Such means may be adapted to regulate the flow rate of active substance in proportion to the speed of travel of the sprayer and/or the plant surface to be treated. The plant surface to be treated may be evaluated using an onboard camera on the ramp or the agricultural vehicle coupled to an image processing system.

In the case where each injector 21 a to 21 d comprises a valve or an electromagnetic or piezoelectric pump, said regulating means are formed by an electronic circuit adapted to vary the vibrational frequency of each injector 21 a to 21 d. The operating mode and the advantages of the present invention result directly from the preceding description.

A liquid to be sprayed is placed in the primary vat 5. This may be either clean water, or a mixture of clean water and a phytosanitary product, or potentially a liquid fertilizer, which must be sprayed in pure state and at a large volume per hectare.

During operation, the primary pump 13 sends the liquid to be sprayed into all of the bodies 3 distributed on the ramp 9, thereby allowing that liquid to be sprayed by the nozzles.

The pump 13 may be of the displacement, constant pressure or constant flow rate type. It may have pistons, membranes, a centrifuge, or other means.

With the injector devices 21, which directly regulate the quantity of active substance per hectare, the pump 13 is kept at a constant pressure. This pressure is selected, in association with the type of nozzles installed, to generate drops with a predetermined size and spectrum, not modified by the speed of travel or the quantity of active substance introduced by the injectors 21.

Exceptionally, when it is preferable to use the sprayer traditionally, without using the injectors 21/221, the pump 13 may then be interfaced with a braking system of the DPA (output proportional to forward speed) type, which makes it possible to adapt the liquid flow rate in the primary conduit 7 as a function of the forward speed of the sprayer.

Mixtures containing active substances designed to be incorporated into the liquid to be sprayed are placed in the secondary vats 25 a to 25 d.

This incorporation is done by acting on the secondary pumps 33 a to 33 d, selectively or simultaneously. This incorporation may also be done by placing the vats 25 a to 25 d under air pressure, or under hydrostatic pressure using pressure exchangers, as mentioned above, inasmuch as pumps 33 a to 33 d are not used, but the injectors 21/221 are rather used directly, which then act as simple dosers.

In so doing, the injectors 21 a to 21 d inject the concerned mixtures of active substances into the body 3, i.e. just upstream from the nozzle 1.

These active substances are therefore incorporated into the liquid coming from the primary vat 5 immediately before spraying, and therefore sprayed on the plants to be treated taking the forward travel speed of the sprayer into account, which prevents overdoses and underdoses.

FIG. 2 shows a second spraying assembly as an alternative to the first spraying assembly illustrated in FIG. 1. In FIG. 2, the components of the second spraying assembly that have a structure and function identical to the components of the first spraying assembly bear the same numerical references and operate comparably, with the exception of the differences indicated below.

Each indicator 221 a to 221 d of this embodiment comprises a piston 223 a and 223 d, controlled by a piezoelectric component 229 a to 229 d arranged inside the body of the injector, which is only partially shown in FIG. 2. This makes it possible to form, within each injector, a piezoelectric micro-pump capable of delivering a predetermined quantity of liquid to the nozzle 1, proportional to its vibrational frequency. In practice, each piston 223 a and 223 d can be made up of one or more surfaces of the piezoelectric component, since the vibrations of such a component cause alternating translations of its surfaces.

Alternatively, the pistons 223 a to 223 d are replaced by membranes controlled by an electromagnetic device. Membrane pumps are then used.

Alternatively, a magnetic or ceramic micro-pump or a peristaltic micro-pump may be used in each injector 221 a to 221 d.

Depending on the type of pump used in the injectors, and its withdrawal power, it is possible to do without the pumps 33 a to 33 d, which are therefore optional, for example by placing the reservoirs 25 a to 25 d under a slight overpressure of several decibars with respect to the conduits 7 and 8, as considered above with a pressure exchanger.

Outlet valves made up of needles 222 a to 222 d are respectively arranged near and downstream from each corresponding injector 221 a to 221 d, so as to close off the outlet orifice 226 a to 226 d. Each needle 222 a to 222 d has a globally conical shape to come alongside a seat with a complementary shape that is formed at the corresponding outlet orifice 226 a to 226 d.

Each needle 222 a to 222 d serves to allow or stop the fluid communication between the injector 221 a to 221 d and the nozzle 1.

The respective needles 222 a to 222 d of the injectors 221 a to 221 d are mounted in opposite directions relative to the needles 22 a to 22 d of the injectors 21 a to 21 d. The needles 222 a to 222 d act as discharge valves, while the needles 22 a to 22 d of the injectors 21 a to 21 d act as opening valves of the respective chamber 21 a to 21 d with respect to the body 3. The needles 22 a to 22 d and 222 a to 222 d also perform a check function in the upstream direction.

Each injector 221 a to 221 d also includes a valve, such as the obturator 224 a, arranged on the corresponding secondary conduit 23 a to 23 d, so as to cut the supply. Such an obturator may also operate in suction. It advantageously forms a check valve.

During operation, when the piston 223 a has withdrawn to suction the active substance in the injector 221 a, the obturator 224 a opens automatically. Then, when the piston 223 a moves forward within the injector 221 a, toward the needle 222 a, the obturator 224 a closes automatically.

When the active substance pressure in the injector 221 a exceeds the force due to the stiffness of a spraying 225 a returning the needle 222 a to the closed position, the latter part opens and the active substance is discharged outside the injector 221 a into the body 3 and toward the nozzle 1, without rising in the primary conduit 7 toward the primary vat 5, due to the presence of the check valve 203.

The injectors 221 a to 221 d have the same structure and operate in the same way as the injector 221 a described above.

Since the valve 207 and each pump can be actuated remotely, it is possible only to control the circulation of active substance and/or drive the spraying of liquid in the presence of plants to be treated.

The agricultural sprayer is triggered by signals detecting plants to be treated, which determine the spraying phases and/or active substance injection phases. Such signals may for example be generated by an image processing system processing images acquired by an onboard camera on the ramp or the agricultural vehicle. In this way, the spraying may be activated, nozzle by nozzle, only in the presence of plants to be treated, by actuating the valves 203, 207 and 224 and/or the injectors 21 a to 21 d or 221 a to 221 d.

Likewise, the injection of active substance from each of the nozzles may be activated, deactivated, or dosed differently, depending on the state of the crop to be treated, for example by infrared imaging, or by the GPS position characterizing the shape and borders of the field, or a surface that has already been treated, or the proximity of a sensitive area to be respected. For example, in particular when a weedkiller is applied, the injection of active substance may depend on whether the plants to be treated are healthy or in poor health, which may be detected by infrared imaging. The control means, for example, a controller, therefore make it possible, using the injectors, to regulate the flow rate of active substance as a function of the state of the plant surface to be treated. Alternatively or additionally, these control means make it possible to regulate the flow rate of active substance as a function of the speed of movement of the sprayer, i.e. the speed of forward movement of a tractor supporting or pulling it.

Irrespective of the embodiment, the spraying assembly can thus operate by recirculation, in particular to keep the liquid in motion, even after its spraying has been partially or completely temporarily interrupted.

In all of the embodiments, in particular those illustrated, the spraying assembly according to the invention makes it possible to incorporate the active substance(s) into the liquid to be sprayed “at the last minute,” i.e., just before actual spraying of that liquid.

It is therefore possible to adapt the dosing of active substance of the liquid to be sprayed instantaneously by controlling, in a suitable manner, i.e. complete, partial or proportional, the injectors 21 a to 21 d or 221 a to 221 d, and consequently to avoid the overdoses or underdoses observed in the assemblies of the prior art.

In fact, the specific volume of each active substance injector 21 a to 21 d or 221 a to 221 d is not in permanent fluid communication with the mixing area of the body 3. Consequently, an injector 21/221, which is physically on the borderline and very close to the mixing chamber 3, which must be very small and turbulent to ensure good homogenization, does not cause inertia in the dosing of the mixture, which allows each nozzle 1 to make quick, even instantaneous, variations in the concentration of that mixture.

It is possible for the injectors 21 a to 21 d or 221 a to 221 d and/or the secondary pumps 33 a to 33 d also to be interfaced with any DPA regulating system of the pump 13, so as also to adapt the quantity of active substance incorporated into the liquid to be sprayed to the speed of movement of the sprayer.

The secondary vats 25 a to 25 d may either contain different mixtures or identical mixtures. In the latter case, it is possible to have a wider variation range for the quantity of a given active substance incorporated into the liquid to be sprayed.

This in fact makes it possible to adapt the quantity of active substance injected into the body 32 at an extended speed variation range of the sprayer for example situated between 3 and 30 km/h.

This may in particular be useful when the active substance(s) to be incorporated into the liquid to be sprayed in the body 3 are incompatible with the phytosanitary product conveyed by that liquid, by means of the pump 13 and the conduit 7, or when said active substance(s) must be incorporated into the liquid to be sprayed at a very small dose and/or only at certain moments.

Another advantage of the spraying assembly according to the invention lies in the fact that once the size of the drops of liquid to be sprayed by the nozzle 1 is chosen, in particular by acting on the liquid pressure in the primary conduit 7 and the type of nozzle, the incorporation of active substances using injectors 21 or 221, at the nozzle 1 or various segments of the ramp 9, has practically no effect on the size of those drops.

In fact, an assembly according to the invention, including used without DPA or pressure variation of the pump 13, implements means, for example, a regulator or valve, for maintaining the pressure of the liquid to be sprayed, which makes it possible to keep the size of the projected drops substantially constant. It is therefore possible to control this drop size, and consequently to optimize the adaptation of spraying to each category of plants.

Furthermore, such an assembly implements means making it possible to regulate the active substance flow rate, and therefore its concentration in the liquid to be sprayed, in proportion to the speed of forward movement of the ramp 9, without, however, altering the flow rate of that carrier liquid itself.

Aside from the size of the drops, which in this case is constant, the user can thus vary, as desired and potentially manually, the concentration of active substance, in a particularly precise and localized manner.

Furthermore, each pressure maintenance means and each means for regulating the flow rate can be actuated individually and independently, which allows “unitary” control of each injector and each nozzle independently of one another, which guarantees that the sprayer can be used flexibly and with a wide spectrum as to the plants to be treated.

According to one aspect of the invention which is optional and which is shown only in FIG. 1, the nozzle 1 comprises a ramp 400 for injecting air in countercurrent in the injectors 21 a to 21 d. More specifically, an air injector 401 a belonging to the ramp 400 emerges in the injector 21 a and is oriented toward the conduit 23 a. Corresponding injectors belonging to the ramp 400 emerge in the other injectors. The ramp 400 is connected to a compressed air source S through a control valve 402.

Thus, at the end of a half-day or a full day of spraying, it is possible for the user to inject, in the injectors 21 a to 21 d, and countercurrent with respect to the normal direction of circulation of the liquid to be sprayed, a sufficient quantity of air to clean said injectors and push the products to be sprayed effectively toward the reservoirs 25 a to 25 d, through the conduits 23 a to 23 d, the obturators 24 a to 24 d, the pumps 33 a to 33 d and the conduits 27 a to 27 d. Thus, the products present in the injectors 21 a to 21 d and in their respective supply means may be recovered at the end of a spraying period. This operation also makes it possible to decrease the quantity of water or liquid product necessary to clean the injectors 21 a to 21 d and their means for supplying products to be sprayed at the end of a spraying operation.

A similar construction, with means for injecting air in countercurrent, may be adopted with the spraying assembly and the sprayer of FIG. 2.

Of course, the present invention is in no way limited to the example described above, which has been provided as an illustration and non-limitingly. 

1-17. (canceled)
 18. A spraying assembly comprising: at least one nozzle for a liquid to be sprayed; at least one active substance injector for injecting an active substance into the liquid, the at least one injector being situated directly upstream from the at least one nozzle and having an outlet orifice; a pump or a pressurized reservoir supplying active substance to the at least one injector; a conduit connecting the at least one injector to the pump or pressurized reservoir; an obturator interposed on the conduit between the least one injector and the pump or pressurized reservoir; and an outlet valve for each of the at least one injectors designed to close the outlet orifice of the or each injector.
 19. The assembly according to claim 18, wherein the or each outlet valve is a needle adapted to come alongside a seat formed at the outlet orifice.
 20. The assembly according to claim 18, wherein the at least one nozzle and the at least one injector are mounted on a same body or two adjacent bodies, a mixture of the liquid to be sprayed with the active substance occurring through turbulence in the same body or the two adjacent bodies.
 28. The sprayer according to claim 25, further comprising an assembly where the at least one nozzle and the at least one injector are mounted on a same body or two adjacent bodies, a mixture of the liquid to be sprayed with the active substance occurring through turbulence in the same body or the two adjacent bodies, and a regulator for regulating the flow rate of active substance in the body or the two adjacent bodies.
 29. The sprayer according to claim 25, further comprising a regulator adapted to regulate the flow rate of active substance in each of the at least one injectors as a function of a displacement speed of the sprayer or a state of a plant surface to be treated.
 30. The sprayer according to claim or 27, wherein the at least one regulator includes a plurality of regulators and the at least one nozzle includes a plurality of nozzles, the plurality of regulators maintaining the pressure of the liquid to be sprayed by the plurality of nozzles, the plurality of regulators being actuated individually and independently of each other.
 31. The sprayer according to claim 25 wherein the at least one injector includes a pump or a piezoelectric, electromagnetic or peristaltic valve, and the sprayer includes a controller adapted to vary an operating speed of the pump or the valve so as to drive a flow rate thereof.
 32. The sprayer according to claim 25, wherein at least one of the secondary conduits is adapted to convey a first type of active substance and at least one other of the secondary conduits is adapted to convey a second type of active substance.
 33. The sprayer according to claim 25, wherein the at least one primary conduit includes at least one valve to control circulation of the liquid to be sprayed and the at least one secondary conduit includes at least one obturator to control circulation of the active substance, the at least one valve and the at least one obturator being able to be actuated remotely.
 34. A method for cleaning a spraying assembly according to claim 24, comprising the steps of: injecting from a quantity of air into each injector, countercurrent from a direction of flow of the active substance in the injector, and pushing part of the active substance that is present in the injector and upstream back toward the pump or pressurized reservoir for the active substance.
 35. The sprayer according to claim 28, wherein each regulator for regulating the flow rate can be actuated individually and independently.
 36. The sprayer according to claim 32, wherein the first type of active substance is an herbicide and the second type of active substance is an insecticide, a fungicide, or a wetting agent. 